Thread rolling die



April 26, 1932. A. FRAYER 1,855,668

THREAD ROLLING DIE Filed July 21, 1930 i 20 threaded.

ing in the direction of arrow Federated Apr. 26, 1932 UNITED STATES PATENT OFFICE LEE A. PRAYER, F KENT, OHIO, ASSIGNOR'TO ROY H. SMITH, OF KENT, OHIO THREAD ROLLING DIE Application filed July 21,

This invention relates to improvements in thread rolling dies, that is, dies for rolling tlirea'ds into bolt and screw blanks and the li e. One object of the invention is the provision of a die so constructed as to reduce the load upon the machine in which it is used and to greatly decrease the wear upon the die and thereby lengthen its life. i Other objects and features of novelty will appear as I proceed with the description of that embodiment of the invention which, for the purposes of the present application, I have illustrated in the. accompanying draw- 1: ings, in which Figure 1 is an elevational View, more or less diagrammatic in character, showing a .pair of dies embodying the invention in operative relation with a pieceof stock to be Fig. 2 is a fragmental plan view of the lower die of 1, lookingin the direction of arrow 2.

Fig. 3is a plan view of the upper die look- Fig. 4 is a side elevational view of .cular die embodying the invention, and

Fig. 5 is an end view of the entering end of the die of Fig. 4.

Dies of the general character herein referred to as previously employed have been so constructed that as the forward endof each individual thread is brought into contact with the work it throws up a small lump of metal which has to be ironed out, so to speak, when that portion 6f the stock comes into contactwith' the other die. To smooth out these lumps of metal not only requires considerable power,.but their engagement with the threads of the dies on the further rotation. of the stock produces local wear on the dies andgreatly shortens the life of the latter.

In threading machines employing dies of this kind, stock of a diameter approximately equal to the pitch diameter of the finished article is ordinarily'employed. I have discovered that if the teeth of the die at the entering end of the latter are reduced or re moved to a level which corresponds approxia cir- 1930. Serial No. 469,601.

mately to the pitch line of the threads of the finished article, these reduced portions will stand in the way of the aforesaid lumps of metal and will deflect that metal sidewise into the grooves between the teeth where it properly belongs. By this simple expedient I have obtained a quite remarkable increase in the life of'a die, a matter of vital importance in the economical operation of thread ing machines, and I have also decreased to a considerable extent the amount of power necessary for the operation of such machines.

In Fig. 1 of the'drawings, 10 and 11 represent fiat upper and lower dies which are adapted to move in the direction of the arrows for rolling threads into apiece of stock indicated at 12. On this figure the root circle of the finished article is indicated at 13, the pitch circle at 14 and the outer circle of the threads at 15. The circumference of the stock used will correspond substantially with the circle 14. The root line of the threads of the dies is indicated at 16 and the outer line at 17. Normally the two die pieces 10 and 11 are caused to move relatively in opposite directions, means being provided to permit the stock 12 to rotate upon its own axis.

As indicated at 18, the teeth of the dies at the entering end of each die are cut away, or

their height otherwise reduced to a level about half the height of the teeth, that is a level corresponding approximately with that of the pitch circle of the finished articles. At the juncture between the reduced and unreduced portions of each tooth, there is preferably a beveled surface 19 which is substantially triangular, as indicated in Fig. 2. Preferably, also, the outer surfaces of the reduced teeth beyond the triangular surfaces 19 are elongatedflat surfaces 20 with parallel sides. In the present instance, these latter surfaces lie in a plane parallel with the lines 16 and 17, but, while this is desirable, I do not regard it as essential. One feature which is essential, however, is that the teeth 5 at or just beyond the surfaces 19 shall be approximately one-half full height.

The reduction in the height of the teeth on the die is effected by a machining or a grinding operation. In performing this operation, I prefer to cut down the height of all teeth beyond a diagonal line 21 across the die near the entering endthereof, although I may position this line 21 so as to leave one or two teeth of full hei ht at the end surface of the die, as shown in %igs. 2 and 3.

In Figs. 4 and 5 I have shown the invention applied to a die 22- having a working face formed on an arc of a circle, the die being adapted to be mounted in a rotating die holder. A pair of holders each carrying a die 22'are connected for rotation in the same direction, the stock being rolled between them in an opposite direction. The two v dies 'of I each pair are duplicates, dies of Fig. 1. View of one of the rotary dies, the greater number of teeth are shown reduced, but at the right there are several teeth which are of full height, just asin the case of the flat dies previously described.

The dies hereindisclosed are mounted in pairs in suitable machines for reciprocating or rotating the dies, as the case may be.

u'st as are the tw o When a piece of stock is engaged by the dies, it rolls upon the reduced portionsof the die threads, the distancebetween these portions in the two dies being the same approximately as .the diameter of the stock. One by one the full height teeth of each die engage and roll threads into the stock, the metal pressed up by the outer half of each thread crowding an equivalent amount of metal into the lower part ofthe groove of the die on either sideof that thread. As the full height teeth advance toward the work and push' their way into the metal of the blank, they do not force a lump of that metal forward as heretofore, because the reduced portions of the teeth are in the wayof such movement. The grooves of thedie on either side of the tooth in question are the only places available'for the displaced metal to go, and hence that is where it does go. Consequently there are no proecting masses of metal thrown up to be In Fig. 5, which is an end.

with the pitch line ofthe threads of the finv ished article.

. 3. In a die for rolling threads, a series of teeth adapted to form threads in stock rolled thereover, the outer portions of certain of the teeth for a substantial distance at the entering end of the die being removed to a level no higher than that which would correspond approximately with the pitch line of the threads of the finished article.

4. In a pair of cooperating dies for rolling threads, aseries of teeth on eachdie having full height portions adapted to form complete threads in stock rolled thereover, and having lower height portions extending'for a substantial distance in advance of said full height portions adapted to engage the work in advance of said full height portions, said lower height portions of the two dies being spaced apart a distance substantially equal to the diameter of the blank and. be-

ing thereby adapted torengage the stock and prevent the throwin up of metal by the forward extremities 0% said full height portions.

r In testimony whereof, I hereunto afiix my signature. v

LEE A. FRAYER.

later pressed down again, as has been the case Y heretofore.

While in the foregoing description and in the accompanying drawings I have disclosed more or less in detail one specific embodiment of the invention, I desire it to be understood claim:

that such detailed disclosure has been resorted to primarily for the purpose of fully il lustrating the invention, .and that it is not to be construed as amounting 'to any limitations upon the scope thereof. I

Having thus 1. In a die for rolling threads, a series of teeth adapted to form threads in stock rolled thereover, the portions of said teeth for a substantial distance at the entering end ofthe die being flatted and reduced to a level approximately corresponding to the pitch line ofthe threads of the finished article, whereby described my invention, I 

